This invention relates generally to apparatus with a mounting arrangement for avoidance of damage due to ground shocks and, more particularly, to voltage surge arresters having frangible elements mounted so as to avoid damage from earthquakes.
While in its broader aspects the invention may be applied to any apparatus subject to shock damage, the description will be particularly directed to electrical apparatus, such as voltage surge arresters or lightning arresters, for mounting in a location subject to earthquakes.
Surge arresters frequently have a large housing of several meters or more in length of an insulating material such as porcelain, with a metal casting in a ring around its lower end attached to its ultimate support. The housing and the metal casting are expensive elements which desirably should survive any disturbance, such as an earthquake, to which they are subjected. If the arrester is rigidly mounted to the ground, it can be placed in mechanical resonance by an earthquake resulting in brittle fracture of the arrester insulator, its base casting, or the joint between them. It can be readily seen that following a natural disaster, such as an earthquake, the maintenance of a satisfactory electrical power system can be vital.
Attention has been previously given to arrester supports that minimize susceptibility to earthquake damage. Examples are U.S. Pat. Nos. 3,794,277 and 3,856,242. A general characteristic of such prior art arrangements is the use of some kind of spring or shock absorber elements for resiliently mounting the arrester. There may be a spring mounting that permits the arrester to "float" at any time, which is subject to the limitation that the spring elements may be subjected to forces beyond their ability to absorb with the result of apparatus breakage. Additionally, the above patents illustrate embodiments in which a breakable or deformable member serves as a primary support that initially maintains rigidity and prevents any significant motion of the supported device. Only after the primary support fails, a secondary resilient spring assembly comes into play. Such arrangements may be disadvantageous where the initial breakable member gives uncertain protection or the spring assembly cannot absorb further shocks.